The present invention relates generally to a sensing arrangement for sensing the addition of reactants into a solution in a tank. More specifically, the invention relates to a sensing arrangement which uses a detector to detect the concentration of the solution as a first reactant is added through a first inlet and mixed with the solution. The detector is positioned adjacent a second inlet and is also used to detect the influx of a second reactant as it is added through the second inlet.
In commercial cleaning systems such as commercial dishwashers, the detergent or chemicals used in the process are sometimes fed into the machine as a two or more part system. For dishwashers this system is typically a two part system made up of a Chemical Energy part and a Chelant part. The Chemical Energy is usually Sodium Hydroxide and water or some other highly caustic liquid and the Chelant is usually a sequestering agent such as NTA, EDTA, or STPP mixed with water. These two parts are mixed in the dishwasher's wash tank to produce a cleaning product that is customized for each situation to match the needs as to soil levels and the water hardness. The Chemical Energy part is adjusted according to the soil levels and the Chelant is adjusted according to the water hardness. The difficulty with this two part approach is that if the ratios of the two part detergent system are not kept within fairly close tolerances, either the amount of the relatively expensive Chelant unnecessarily increases therefore increasing the operating costs or the dishwasher scales up if not enough Chelant is used.
The present invention discloses a novel sensing arrangement which is used to provide feedback information to a reagent supply controller. The controller uses this sensed information to control the amounts of chemicals added to the solution.